JP2019532512A - Apparatus and method for anisotropic DRIE etching using fluorine gas mixture - Google Patents

Abstract

The present invention relates to an etching method for anisotropically structuring a substrate (101) using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. According to the present invention, a fluorine gas mixture comprising more than 25% fluorine at a rate of up to 40%, nitrogen at a rate of 1% to 50%, and a rare gas at a rate of 30% to a maximum of 60% is etched. used. The invention also relates to the use of such a fluorine gas mixture and to an apparatus (300) for structuring a substrate (101, 302) using the fluorine gas mixture of the invention.

Description

  The present invention is a method for deep reactive ion etching (DRIE) using a fluorine gas mixture having the features of claim 1 and for deep reactive ion etching having the features of claim 10. And a device having a reactor for deep reactive ion etching using the fluorine gas mixture of the present invention having the features of claim 12.

  In order to manufacture a semiconductor device or a MEMS (Micro Electromechanical Structure) system, a substrate is structured. Various etching processes can be used for this purpose. A wet chemical etching method and a dry etching method are known, and the latter is divided into a chemical process and a physical process.

  A chemical dry etching (CDE) process involves a chemical reaction between neutral particles / molecules (usually radicals) and the substrate surface, which results in the structuring of the substrate. Radicals are generated in the plasma, which is why chemical dry etching is commonly referred to as plasma etching. Chemical dry etching processes generally exhibit very isotropic etching behavior.

  On the other hand, physical dry etching methods exhibit rather anisotropic etching patterns. In this case, the substrate surface is etched by collision with ions, electrons or photons. The processes involved in structuring the substrate are similar to those involved in sputtering. However, physical dry etching methods generally have a relatively slow etch rate and even a low material selectivity. Etching accompanied by a mask results in rounded edges. Moreover, high energy is required for etching in order for ions to penetrate deep into the material. Thus, not only is etching performed on the surface, but deeper layers are also damaged. Another disadvantage is that the etched particles are parasitically deposited (re-deposited) on the substrate, the mask, or the edge of the mask.

  A mixed form of two dry etching methods combining the advantages of chemical dry etching and physical dry etching is a physicochemical dry etching method, which is generally called plasma-assisted etching. In general, educts are activated or radicalized by plasma and then induced on the substrate by ion acceleration. Well-known representative examples of the physicochemical dry etching method are reactive ion etching (RIE) and deep reactive ion etching (DRIE). Deep reactive ion etching (DRIE) is also known as the Bosch process.

  In all the above etching methods, a dedicated gas or gas mixture is used as the etching gas. Each etching gas is dedicated to each etching method. In particular, in the case of gas mixtures, the selected etching method may no longer be feasible with a shift of only 1% of each gas component.

For example, sulfur hexafluoride SF ₆ is because it allows a very good and reproducible process control, SF ₆ is used as an etching gas for deep reactive ion etching. In addition, sulfur hexafluoride SF ₆ is easy to handle and relatively non-toxic.

However, sulfur hexafluoride SF ₆ is a gas extremely harmful to the environment, and its GWP (Global Warming Potential) value is> 22800, which greatly contributes to global warming (“climate killer” "). In addition, in continuous operation, the etching facility stores a large amount of partially reacted sulfur compounds in the reactor vacuum pump line. This is undesirable in 24 hour operation and leads to relatively high maintenance costs.

  An object of the present invention is to make deep reactive ion etching for anisotropic structuring of a substrate more environmentally friendly while maintaining the characteristic etching characteristics of the method.

  According to the invention, this problem is solved by an etching method having the features of claim 1.

The etching method of the present invention comprises anisotropically structuring a substrate using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. According to the present invention, a proportion of fluorine of more than 25% and a maximum of 40% (25% <F ₂ ≦ 40%), nitrogen of 1% to 50% (1% ≦ N ₂ ≦ 50%), A fluorine gas mixture having a rare gas ratio (30% ≦ noble gas ≦ 60%) of 30% up to 60% is used for etching. This particular composition of the fluorine gas mixture of the invention is extremely suitable to replace SF ₆ which has been used conventionally. The present invention shows that, according to prior knowledge, F ₂ fluorine gas mixtures exhibit strong isotropic etching behavior, ie, contrast to fluorine-containing molecules (eg, CF ₄ , CHF ₃ , C ₄ F ₈ etc.). In particular, the F ₂ fluorine gas mixture is not suitable for realizing a fine structure in the nanometer range, for example, a semiconductor device, and has high selectivity to the side wall (= very smooth side of the structure to be generated). Is based on the fact that pure reactive ion etching with Therefore, the F ₂ fluorine gas mixture is used only for cleaning the CVD system, and the F ₂ fluorine gas mixture is poured into the CVD system and an isotropic etching behavior is desired. Almost all conventional plasma systems used to microstructure semiconductor devices and MEMS devices using a photoresist mask have a corresponding selectivity to the mask and an undesirable “undercut” (= the layer to be etched). Continuous sidewall passivation is always required to prevent under-etching). However, this can be usually used a polymerization gas such CHF ₃ alone. In this regard, the F ₂ gas mixture, with its high radical density, performs only isotropic etching without additional polymerizing gas, ie undercuts, and is considered for anisotropic etching. As it is not possible, the F ₂ gas mixture is not usable for this purpose or can only be used in a very limited way. However, according to the gas composition according to the present invention, contrary to conventional assumptions, an F ₂ fluorine gas mixture can be used to anisotropically structure the substrate.

  As mentioned at the outset, in the DRIE etching method, a gas composition shift in the range of only 1% can lead to a significant change in the etching rate, ie the feasibility of the method. As a result of experiments, surprisingly, fluorine gas having 35% to a maximum of 40% fluorine, 1% to 50% nitrogen, and 30% to 59% rare gas. It has been found that the mixture gives significantly better results in terms of etch rate and process control than the theoretical prediction of this composition.

  It is envisioned that the fluorine gas mixture includes a noble gas from the group consisting of argon, neon, krypton, helium, radon, and xenon.

According to one embodiment, the fluorine gas mixture may comprise only argon as a noble gas component. The use of argon in combination with F ₂ and N ₂ has been shown to give particularly good results in etching using the method of the present invention.

According to another embodiment, the passivation step includes applying a passivation layer on the substrate by using C ₄ F ₆ as the process gas. Currently, C ₄ F ₈ polymerizing gas is used for passivation in existing DRIE processes. However, this C ₄ F ₈ polymerized gas is extremely harmful to the environment, and its GWP (Global Warming Potential) is 8700. On the other hand, C ₄ F ₆ polymerizing gas is much more environmentally friendly and the process gas has a GWP of 1. Thus, replacing C ₄ F ₈ with C ₄ F ₆ in the present invention further contributes to solving the problem of the present invention, that is, making the existing DRIE process much more environmentally friendly.

  In particular, according to embodiments of the present invention, the method includes generating reactive ions in a high frequency direct plasma. In direct plasma as opposed to so-called remote plasma, the plasma is generated directly in the etching chamber. High frequency direct plasma is understood as plasma generated at an excitation frequency of 3 MHz to 300 GHz.

  Here, it is envisaged that the method includes generating reactive ions in a high frequency direct plasma inductively or capacitively coupled with an excitation frequency in a short wave frequency band in the frequency range of 3 MHz to 30 MHz. The preferred high frequency range ranges from 10 MHz to 15 MHz. For example, the selected frequency is 13.56 MHz.

According to a further embodiment of the present invention, the method includes generating reactive ions in a high frequency plasma with an excitation frequency in a microwave frequency band within a frequency range of 0.3 GHz to 3 GHz. The preferred high frequency range ranges from 2 GHz to 3 Ghz. For example, the selected frequency is 2.45 GHz. In existing DRIE processes using SF ₆ as the etching gas, microwave excitation is not used. Because, for example, a microwave excitation at 2.5GHz is not suitable for a heavy gas which like SF _6, high frequency power necessary to decompose SF ₆ in F radicals is very complex and inadequate way This is because it can be combined only with. In combination with the present invention using an F ₂ fluorine gas mixture as the etching gas, the use of microwave excitation is synergistically very interesting. The fluorine gas mixture is already decomposed into fluorine radicals at a power density that is one-third that of the above, thus enabling a high fluorine radical density even with microwave excitation. Thus, microwave plasma produces very high radical densities at relatively low energy inputs, particularly when using fluorine gas mixtures, resulting in significantly higher F radical densities.

  In order to obtain sufficiently good etch uniformity across a silicon substrate (diameter 200-300 mm) using microwave excitation, in a further embodiment, a plurality of individually controlled microwave coupling sources arranged regularly and flatly. And mask frequency or silicon uniformity of the ablation rate can be optimized by maximum frequency power control.

  According to a further embodiment, the method of the invention comprises generating reactive fluorine ions and fluorine radicals, generating more reactive fluorine ions than fluorine radicals during a first period, During two periods, more fluorine radicals are generated than reactive fluorine ions. Reactive fluorine ions are required to penetrate the passivation layer or polymerized layer. On the other hand, radicals etch the substrate to be structured with high selectivity. Thus, according to the present invention, reactive fluorine ions are first generated at the beginning of the etching step (eg, 0.5 seconds) and then directed onto the substrate to break through the passivation layer applied in the previous passivation step. Fluorine radicals are then generated and directed onto the exposed substrate to etch or structure the substrate. For example, the generation of radicals and reactive ions in a particular time window can be achieved using a controller connected to the plasma source, which can be used to generate fluorine radicals in the plasma at different points in time. And the plasma source are configured to produce different distributions of the proportion of fluorine ions.

A further aspect of the invention is the use of a fluorine gas mixture for anisotropically structuring a substrate using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. And the fluorine gas mixture is more than 25% up to 40% fluorine (25% <F ₂ ≦ 40%) and 1% to 50% nitrogen (1% ≦ N ₂ ≦ 50). %) And a noble gas (30% ≦ noble gas ≦ 60%) in a ratio of 30% to a maximum of 60%.

A further aspect of the invention comprises a reactor for anisotropically structuring a substrate using deep reactive ion etching (DRIE), in which etching steps and passivation steps are alternately performed a plurality of times, and a reaction The apparatus includes a gas inlet for supplying an etching gas into the vessel, and the etching gas includes fluorine at a ratio of more than 25% and a maximum of 40% (25% <F ₂ ≦ 40%), 1 Fluorine gas mixture having a nitrogen to 1% ratio of 50% to 1% (1% ≦ N ₂ ≦ 50%) and a rare gas ratio of 30% to a maximum of 60% (30% ≦ noble gas ≦ 60%) is used. The

  Embodiments of the invention are described below and illustrated in the drawings.

FIG. 2 shows a schematic cross-sectional view of a substrate structured using the method of the present invention. 1 shows a conventional plasma system for deep reactive ion etching using SF ₆ as a process gas according to the prior art. 1 shows a plasma system of the present invention for deep reactive ion etching using a fluorine gas mixture of the present invention as a process gas.

  FIG. 1 schematically illustrates an etching pattern of a substrate 101 structured using the DRIE process of the present invention. The DRIE process is also commonly referred to as a Bosch process.

  The specificity of the Bosch process varies regularly between isotropic Si etching and isotropic polymerisation, with a relatively small anisotropy at each Si etching step, mainly at the beginning of each Si etching step. It is necessary. Although each etching step can be isotropic, the structure 104 etched into the substrate 101 exhibits high anisotropy due to alternating etching and polymerizing steps.

  The silicon substrate 101 exemplarily shown in FIG. 1 also has a passivation layer (eg, oxide) 102. The repeated passivation steps described above also result in additional passivation or polymer layer 103 on substrate 101. This polymer layer 103 also provides bottom and sidewall passivation within the cavity 104.

The Bosch process alternates with a combination of reactive ion etching and polymer deposition to produce deep trenches, cavities, or TSVs (Through Silicon Vias) 104 in the silicon substrate 101. At present, in the Bosch process according to the prior art, C ₄ F ₈ gas is used for polymer deposition and SF ₆ etching gas is used for actual Si etching.

The traditional Bosch process consists essentially of the following three process steps:
(A) Isotropic chemical etching using F radicals (formed from SF ₆ );
(B) Surface passivation with C ₄ F ₈ gas without isotropic RF bias;
(C) Removal of bottom passivation using accelerated ions (physical etching).

  All etching chambers used in the prior art use so-called inductively coupled plasma excitation at a frequency of 13.56 MHz, paired with an additional plasma source at a frequency of 13.56 MHz or 400 kHz applied at the same time. A so-called DC bias or acceleration voltage is generated through the cathode.

The inductively coupled plasma at the top of the reactor produces relatively dense and non-directed fluorine ions and fluorine radicals, and isotropically silicon is mainly caused by the high radical density produced. % Etch. A superimposed second plasma source accelerates SF _x ions perpendicularly toward the wafer surface and is controlled independently of the induction source to produce an anisotropic etch.

  The anisotropic etch is only needed to break through the thin Teflon-like polymer layer 102 previously deposited at the bottom of the resulting groove 104 (the polymer is held on the sidewall of the groove 104). Thus, the next isotropic Si etching by fluorine radicals is enabled by preventing undercut).

Polymerization is obtained by igniting a C ₄ F ₈ plasma and “depositing” a thin layer of PTFE by only applying 13.56 MHz power inductively coupled without bias RF.

The SF ₆ etching gas used in the conventional Bosch process is extremely harmful to the environment, and its GWP (global warming potential) value is> 22800, which greatly contributes to global warming ("climate killer") ). In addition, during the continuous operation of the etching facility, large amounts of partially reacted sulfur compounds accumulate in the reactor vacuum pump line. This is undesirable in 24-hour operation and leads to relatively high maintenance costs.

Thus, the present invention specifically produces a lithographically defined deep structure 104 in a substrate (eg, bulk silicon) 101 with an aspect ratio greater than 20: 1 (aspect ratio = depth / trench width). In order to make this possible, it is proposed to replace the SF ₆ etching gas conventionally used in the Bosch process with a fluorine gas mixture.

According to the present invention, the fluorine gas mixture comprises more than 25% and up to 40% fluorine (25% <F ₂ ≦ 40%) and 1% to 50% nitrogen (1% ≦ N ₂ ≦ 50%) and 30% to a maximum of 60% noble gas (30% ≦ noble gas ≦ 60%). Argon is preferably used as a rare gas.

  Particularly good results can be obtained with a fluorine gas mixture comprising 35% up to 40% fluorine, 1% up to 50% nitrogen and 30% up to 59% noble gas.

Also, the fluorine gas mixture can be used to optimize the required selectivity and anisotropic etch rate, with the concentration of F ₂ / noble gas (He, Ar, Neon, Krypton, xenon) / N ₂ .

  At present, the fluorine gas mixture is known to have very high isotropic properties, that is, the fluorine gas mixture is mostly etched without directionality. Therefore, the fluorine gas mixture is very suitable as a cleaning gas for cleaning a CVD chamber, for example. The fluorine gas mixture flows into the CVD chamber and is distributed over most of the chamber to perform isotropic etching and remove residues from the chamber walls. That is, this high isotropy is desirable for cleaning. However, according to general expertise, fluorine gas mixtures are not suitable for directional structuring of substrates due to their high isotropy.

In contrast to the CVD cleaning plasma, where the F ₂ gas mixture is used, for example, to remove the entire glass layer or amorphous silicon layer on the CVD reactor wall, the present invention uses SF ₆ gas that has been used exclusively in the environment. At the same time as replacing for reasons, the F ₂ gas mixture can be structured and substrate (eg, for example) with the above objective that the lifetime of the etch chamber and vacuum components can be extended by preventing the sulfur deposition from interfering with them. The first use for a silicon wafer will be explained.

To replace SF ₆ with an environmentally friendly F ₂ gas mixture in DRIE etching of silicon structured with a photomask, a CVD cleaning process in which the fluorine gas mixture is directed into the chamber chamber without direction so that it flows into the chamber chamber; Different technical methods are also required. Apart from this point, the composition (percentage distribution) of each gas component of the fluorine gas mixture used in the CVD cleaning process is different from the composition of the fluorine gas mixture according to the present invention. It should be noted that in the case of a fluorine gas mixture, the desired method can no longer function with a deviation of only 1% of one type of mixing component.

In DRIE etching, in order to be able to perform actual Si etching, the selectivity required for a Teflon-like polymer layer and the minimum anisotropy when breaking through the layer are required. The addition of N ₂ and a noble gas (eg, argon as a relatively heavy atom) to the F ₂ gas mixture to repeatedly open the prepolymerized groove bottom. This is a new solution to be able to obtain the required sputtering energy.

The use of F ₂ gas mixture, instead of 100% F _2, to 100% of F ₂ are are highly reactive and pyrophoric, it is advantageous for safety reasons. Also, 100% F ₂ does not provide the silicon selectivity required for conventional masking layers such as Si glass, silicon nitride, photoresist, etc. This is because a fluorine gas mixture is used in reactive ion etching. This is another reason that did not come.

  The method of the present invention can be implemented in conventional inductively coupled plasma (eg, plasma at 13.56 MHz) or using microwave plasma (eg, plasma at 2.45 GHz).

  There are many advantages to using the fluorine gas mixture of the present invention in combination with microwave plasma.

  For example, microwave plasmas produce very high radical densities at relatively low operating energy, especially when fluorine gas mixtures are used, significantly higher fluorine radicals compared to plasmas excited at low frequencies. Bring density.

As an advantage of the apparatus of the present invention, an inductively coupled plasma (eg, 13.56 MHz) is not required when using microwaves to form F ₂ radicals, since no additional matching unit (electromechanical high frequency tuning unit) is required. ), It can be constructed more reliably than the process chamber currently used.

C ₄ F ₈ polymerizing gas can still be used. However, C ₄ F ₈ for passivation and SF ₆ etching gas for prior art etching are extremely harmful to the environment. Thus, according to the present invention, it is conceivable to use C ₄ F ₆ and SF ₄ as possible alternatives to C ₄ F ₈ and SF ₆ . Compared to C ₄ F ₈ (C ₄ F ₈ GWP = 8700), C ₄ F ₆ has only 1 GWP (C ₄ F ₆ GWP = 1).

  Only the latest design microwave source coupled to the ceramic surface of multiple adjacent ceramic waveguides has the flat and evenly distributed radical density required across the wafer surface to obtain uniform Si removal. Cause it to occur.

  Further optimization of the achievable uniformity of silicon substrates in the diameter range of 200 mm to 300 mm in a more complex way of combining a plurality of individually controllable microwave sources arranged in a matrix and regularly distributed Can be realized. The application of individually controllable microwave power for each coupling element allows the ion energy distributed across the etching chamber and the radical density distributed across the etching chamber to be measured across the reactor in order to obtain as uniform etch ablation as possible. Over which it can be applied very accurately.

To allow a 13.56 MHz or 400 kHz second RF generator to produce tunable and precisely controllable ion acceleration (sputter etch step) at the polymer opening towards the cathode or wafer surface, respectively. Only needed. The fluorine gas mixture of the present invention is very easily decomposable and requires relatively low RF power to produce a fluorine radical density comparable to SF ₆ , ie, a high Si etch rate.

  In the method of the present invention, fluorine ions are advantageously available for breaking through the passivation layer or polymerized layer 103, and fluorine radicals are desired to structure the substrate 101 (passivation layer or polymer temporary layer 103). After breaking through).

  Thus, according to embodiments of the present invention, the method of the present invention includes generating reactive fluorine ions and fluorine radicals, generating more reactive fluorine ions than fluorine radicals during the first period, More fluorine radicals are generated than reactive fluorine ions during the subsequent second period.

  Reactive fluorine ions are required to penetrate the passivation layer or polymerized layer 103. On the other hand, fluorine radicals etch the substrate to be structured with high selectivity. Thus, according to the present invention, reactive fluorine ions are first generated at the beginning of the etching step (eg, over 0.5 seconds) and then directed onto the substrate 101 and applied to the passivation layer applied in the previous passivation step. Alternatively, the polymerized layer 103 is broken through. Next, fluorine radicals are generated and guided onto the exposed substrate 101 to etch or structure the substrate 101.

  For example, the generation of radicals and reactive ions within a specific time window can be achieved using a controller connected to the plasma source, which can be combined with fluorine radicals in the plasma at different points in time. It is configured to control the plasma source to produce different distributions of the proportion of fluorine ions.

  For example, the controller can be configured to increase the excitation frequency for generating plasma as a function of time. At high frequencies below the microwave frequency range, i.e., frequencies from approximately 30 MHz to 300 MHz, both radicals and reactive ions are formed in the plasma. At frequencies in the microwave frequency range, i.e., frequencies of approximately 0.3 GHz to 3 GHz, ions can no longer accompany and only radicals are formed in the plasma.

  Accordingly, the controller generates plasma at the first excitation frequency during the first period, generates plasma at the second excitation frequency during the second period, and the first excitation frequency is lower than the second excitation frequency, One excitation frequency is preferably less than the microwave frequency range, i.e., approximately 30 MHz to 300 MHz, and the second excitation frequency is in the microwave frequency range of 0.3 GHz to 3 GHz.

FIG. 2 shows a conventional plasma system 200 for deep reactive ion etching according to the prior art. The plasma system 200 includes a process chamber 201 that includes a substrate 202 to be structured. In addition, the plasma system 200 includes a chamber provided with a plasma source 203, and SF ₆ can be introduced into the chamber as a process gas 204 through a gas inlet 205. Process gas 204 (here SF ₆ ) is directed to plasma source 203 via upstream mass flow controller 206.

In order to use the fluorine gas mixture of the present invention so that high safety requirements can be met, the conventionally used plasma system as shown in FIG. 2 must be modified or new Reactors must be designed and the F ₂ gas mixture is toxic and highly corrosive, so that the fluorine gas mixture according to the present invention can be used without safety concerns.

  Accordingly, as shown in FIG. 3, a plasma system 300 having a suction device 307 for a mass flow controller 306 (MFC, mass flow controller) is proposed. The fluorine gas mixture 304 is carried into the process chamber or vacuum chamber 301.

  FIG. 3 shows a plasma system 300 of the present invention for deep reactive ion etching. The plasma system 300 includes a plasma chamber 301 that includes a substrate 302 to be structured. The plasma system 300 further includes a chamber having a plasma source 303. Compared to the prior art (FIG. 2), the fluorine gas mixture of the present invention used as the process gas 304 is guided into the plasma chamber 300 of the present invention via the gas inlet 305. The fluorine gas mixture is guided to the plasma source 303 via the upstream mass flow controller 306, which is additionally provided with the suction device 307 described above.

  Both plasma systems 200, 300 are common in that the substrate 202, 302 to be structured is placed on the electrode 208, 308 and the ion or gas flow 209, 309 is directed to the substrate (high anisotropy). ing. Moreover, both plasma systems 200 and 300 have connection parts 210 and 310 for vacuum pumps.

300 Plasma System 301 Plasma Chamber 302 Substrate 303 Plasma Source 304 Process Gas 305 Gas Inlet 306 Mass Flow Controller 307 Suction Device 308 Electrode 309 Ion or Gas Flow 310 Connection

Both plasma systems 200, 300 are common in that the substrate 202, 302 to be structured is placed on the electrode 208, 308 and the ion or gas flow 209, 309 is directed to the substrate (high anisotropy). ing. Moreover, both plasma systems 200 and 300 have connection parts 210 and 310 for vacuum pumps.
Additional embodiments and aspects of the invention are described below, but can be used individually or in combination with any of the features, functions, and details described herein.
According to the first aspect, the etching method comprises anisotropically structuring the substrates 101 and 302 using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. A fluorine gas mixture comprising more than 25% up to 40% proportion of fluorine, 1% to 50% proportion of nitrogen and 30% to up to 60% proportion of noble gas is used for etching. ,
According to a second embodiment, which refers to the first embodiment, the fluorine gas mixture is a 35% to a maximum of 40% proportion of fluorine, a 1% to 50% proportion of nitrogen and a 30% to a maximum proportion of 59% of the rare gas. With gas.
According to a third aspect referring to the first aspect or the second aspect, the fluorine gas mixture comprises a noble gas in the group consisting of argon, neon, krypton, helium, radon, and xenon.
According to a fourth aspect referring to the first aspect or the second aspect, the fluorine gas mixture comprises argon as a noble gas component.
According to a fifth aspect refers to the fourth aspect of the first embodiment, the passivation step comprises applying a passivation layer on the substrate 101, 302 with SF ₄ or C ₄ F ₆ as the process gas.
According to a sixth aspect referring to the first aspect to the fifth aspect, the method comprises generating reactive ions in the high frequency direct plasma.
According to a seventh aspect, which refers to the sixth aspect, the method comprises a shortwave frequency band in the frequency range from 3 MHz to 30 MHz, preferably in the range from 13 MHz to 15 MHz, particularly preferably in the range from 13.5 MHz to 13.6 MHz. Generating reactive ions in a high frequency direct plasma that is inductively or capacitively coupled at the excitation frequency of.
According to an eighth aspect referring to the first aspect to the sixth aspect, the method is in the frequency range of 0.3 GHz to 3 GHz, preferably in the frequency range of 0.8 GHz to 2.6 GHz, particularly preferably 2.45 GHz. Generating reactive ions in the high frequency plasma at an excitation frequency in the microwave frequency band of
According to a ninth aspect, which refers to the first aspect to the eighth aspect, the method comprises generating reactive ions and radicals, and generating more reactive ions than radicals during the first period. During the subsequent second period, more radicals are generated than reactive ions.
The tenth aspect is the use of a fluorine gas mixture for anisotropically structuring the substrates 101, 302 using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. The fluorine gas mixture comprises more than 25% up to 40% fluorine, 1% to 50% nitrogen and 30% up to 60% noble gas. The gas is a noble gas from the group consisting of argon, neon, krypton, helium, radon, and xenon.
In the eleventh aspect, which refers to the tenth aspect, the fluorine gas mixture comprises 35% to a maximum of 40% fluorine, 1% to 50% nitrogen, and 30% to 59% rare. With gas.
An apparatus 300 according to the twelfth aspect is a reactor for anisotropically structuring a substrate 302 using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times. 301 and a gas inlet 305 for supplying an etching gas 304 into the reactor 301. The etching gas 304 includes fluorine at a ratio of more than 25% and a maximum of 40%, and 1% to 50%. A fluorine gas mixture with a proportion of nitrogen and a proportion of noble gas of 30% up to 60%.
According to a thirteenth aspect, which refers to the twelfth aspect, the fluorine gas mixture comprises a proportion of 35% to a maximum of 40% fluorine, a ratio of 1% to 50% of nitrogen, and a ratio of 30% to a maximum of 59%. With noble gas.
According to a fourteenth aspect referring to the twelfth aspect or the thirteenth aspect, the fluorine gas mixture 304 comprises at least one noble gas of the group consisting of argon, neon, krypton, helium, radon, and xenon. .
According to the fifteenth aspect referring to the twelfth aspect or the thirteenth aspect, the fluorine gas mixture 304 comprises only argon as a rare gas component.
According to a sixteenth aspect referring to the twelfth aspect to the fifteenth aspect, the apparatus 300 comprises a plasma source 303 configured to generate reactive ions in the high frequency direct plasma.
According to the seventeenth aspect, which refers to the sixteenth aspect, the plasma source 303 is in the frequency range of 3 MHz to 30 MHz, preferably in the range of 13 MHz to 15 MHz, particularly preferably in the range of 13.5 MHz to 13.6 MHz. Reactive ions are generated in a high frequency direct plasma inductively coupled or capacitively coupled at an excitation frequency in the short wave frequency band.
According to the eighteenth aspect, which refers to the twelfth aspect to the sixteenth aspect, the apparatus 300 is preferably in the frequency range of 0.3 GHz to 3 GHz, preferably in the frequency range of 0.8 GHz to 2.6 GHz. Comprises a plasma source 303 configured to generate reactive ions in a high frequency plasma at an excitation frequency in the microwave frequency band of a frequency of 2.45 GHz.
According to the nineteenth aspect, which refers to the sixteenth aspect to the eighteenth aspect, the plasma source 303 includes a plurality of individually controllable microwave sources that are regularly distributed in a matrix and arranged flat.

Claims (19)

An etching method comprising:
Comprising anisotropically structuring the substrate (101, 302) using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times,
A method in which a fluorine gas mixture comprising more than 25% up to 40% proportion of fluorine, 1% to 50% proportion of nitrogen and 30% to up to 60% proportion of noble gas is used for etching. .   The said fluorine gas mixture comprises 35% to a maximum of 40% proportion of fluorine, 1% to 50% of a proportion of nitrogen, and 30% to a maximum of 59% of a noble gas. Method.   The method of claim 1 or 2, wherein the fluorine gas mixture comprises a noble gas from the group consisting of argon, neon, krypton, helium, radon, and xenon.   The method according to claim 1 or 2, wherein the fluorine gas mixture comprises argon as a noble gas component. The passivation step, with SF ₄ or C ₄ F ₆ as a process gas comprising applying a passivation layer on the substrate (101, 302), according to any one of claims 1 to 4 way .   6. A method according to any one of the preceding claims, comprising generating reactive ions in a high frequency direct plasma.   In a high frequency direct plasma inductively or capacitively coupled with an excitation frequency in the short wave frequency band in the frequency range of 3 MHz to 30 MHz, preferably in the range of 13 MHz to 15 MHz, particularly preferably in the range of 13.5 MHz to 13.6 MHz. 7. The method of claim 6, comprising generating reactive ions in   Reactive ions in a high frequency plasma at an excitation frequency in the microwave frequency band of 0.3 GHz to 3 GHz, preferably in the frequency range of 0.8 GHz to 2.6 GHz, particularly preferably in the microwave frequency band of 2.45 GHz. 7. A method according to any one of claims 1 to 6 comprising generating.   Generating reactive ions and radicals, generating more reactive ions than radicals during the first period and generating more radicals than reactive ions during the subsequent second period A method according to any one of claims 1 to 8.   The use of a fluorine gas mixture to anisotropically structure a substrate (101, 302) using deep reactive ion etching (DRIE), in which etching steps and passivation steps are alternately performed a plurality of times. The fluorine gas mixture comprises more than 25% fluorine at a maximum rate of 40%, nitrogen at a rate of 1% to 50%, and a rare gas at a rate of 30% to a maximum of 60%, Is a noble gas from the group consisting of argon, neon, krypton, helium, radon, and xenon.   11. The fluorine gas mixture comprises 35% to a maximum of 40% proportion of fluorine, 1% to 50% proportion of nitrogen, and 30% to a maximum of 59% proportion of a noble gas. use. A reactor (301) for anisotropically structuring the substrate (302) using deep reactive ion etching (DRIE) in which etching steps and passivation steps are alternately performed a plurality of times;
A gas inlet (305) for supplying an etching gas (304) into the reactor (301), more than 25% up to 40% fluorine and 1% to 50% An apparatus (300), wherein a fluorine gas mixture comprising nitrogen and a noble gas in a proportion of 30% up to 60% is used as the etching gas (304).   13. The fluorine gas mixture of claim 12, comprising 35% to a maximum of 40% fluorine, 1% to 50% nitrogen, and 30% to 59% noble gas. Device (300).   The apparatus (300) of claim 12 or 13, wherein the fluorine gas mixture (304) comprises at least one noble gas of the group consisting of argon, neon, krypton, helium, radon, and xenon.   14. Apparatus (300) according to claim 12 or 13, wherein the fluorine gas mixture (304) comprises only argon as a noble gas component.   16. Apparatus (300) according to any one of claims 12 to 15, comprising a plasma source (303) configured to generate reactive ions in a high frequency direct plasma.   The plasma source (303) is inductively coupled or capacitive at an excitation frequency in a short frequency band within a frequency range of 3 MHz to 30 MHz, preferably within a range of 13 MHz to 15 MHz, particularly preferably within a range of 13.5 MHz to 13.6 MHz. The apparatus (300) of claim 16, wherein the apparatus (300) is configured to generate reactive ions in a coupled high frequency direct plasma.   Reactive ions in a high frequency plasma at an excitation frequency in the microwave frequency band of 0.3 GHz to 3 GHz, preferably in the frequency range of 0.8 GHz to 2.6 GHz, particularly preferably in the microwave frequency band of 2.45 GHz. The apparatus (300) according to any one of claims 12 to 16, comprising a plasma source (303) configured to be generated.   19. Apparatus (300) according to any one of claims 16 to 18, wherein the plasma source (303) comprises a plurality of individually controllable microwave sources arranged in a regular matrix and arranged flat. ).

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